1. Field of Invention
The present invention relates generally to thermodynamic turbine mapping for turbochargers and, more specifically, to a method of extended thermodynamic turbine mapping via compressor inlet throttling for a turbocharger.
2. Description of the Related Art
It is known to provide a turbocharger for an engine of a vehicle such as an automotive vehicle. An automotive turbocharger typically consists of a compressor and a turbine on a common shaft supported by bearings in a center housing. The turbocharger extracts some of the energy in the exhaust gas, and transfers this power to the compressor. The compressor increases the intake air density, and thereby the engine power. Turbocharger performance is usually presented in maps using corrected performance variables. The corrections are important since the performance maps are otherwise only valid for the conditions under which they were measured. Turbocharger performance may be measured on an engine in a test stand.
It is also known to provide extended thermodynamic turbine mapping of a turbocharger. Extended turbine maps are needed as inputs to numerical engine power simulations. Extended thermodynamic turbine maps provide more accurate inputs to engine power simulations. In the absence of extended thermodynamic turbine maps, existing thermodynamic maps are extrapolated, and this practice is inaccurate, leading to false assumptions about turbocharger-engine system performance. Existing methods to obtain extended thermodynamic turbine maps require expensive equipment or dedicated facilities.
It is further known to provide a method for functional testing of turbochargers. An example of such a method is disclosed in U.S. Patent Application Publication No. 2014/0007663 to Berger. In this method, exhaust gas turbocharger are subjected to pressurized gas and operated thereby. The test turbocharger is integrated in a testing device and is subjected by means of this testing device only in a pulse-like manner to a gas, preferably compressed air, wherein from the dynamic behavior of the test turbocharger resulting from the at least one gas pressure pulse, potential errors are determined.
However, it is desirable to accurately characterize turbine performance over a wide range of expansion ratios. To accomplish this, it is known to provide a compressor closed loop unit (CCLU) as a means to extend thermodynamic turbine maps for turbochargers. However, this CCLU is more expensive and complex to retrofit to existing gas test stand, which is undesired. Further, current extended thermodynamic turbine maps obtained on conventional gas stand test stands can only span a narrow subset of the expansion ratio.
Therefore, it is desirable to provide a new method to obtain extended thermodynamic turbine maps for turbochargers on existing gas stand test benches. It is also desirable to provide a method that is capable of changing an inlet density for a compressor of a turbocharger to extend thermodynamic turbine maps for turbochargers. It is further desirable to provide a method that can be implemented on any conventional gas test stand at low cost. Thus, there is a need in the art to provide a method of extended thermodynamic turbine mapping via compressor inlet throttling for a turbocharger.